1. Field of the Invention
The present invention relates to reinforced, cold formable panel structures having a panel core formed from a cementitious composition. Such panel structures have many applications in the building and construction industries when used in their planar configuration since they have properties similar to plywood. However, they also may be bent or otherwise cold formed to many different arcuate configurations to make a wide variety of reinforced concrete articles or structures having shapes which ordinarily are formed before the cementitious composition has cured.
The present invention also relates to methods for producing these cold formable reinforced panel structures which can be either cold formed or used in their planar configuration.
2. Description of the Prior Art
Reinforced panel structures having panel cores formed of a cementitious composition are presently known. U.S. Pat. No. 1,439,954 (Emerson) discloses a gypsum wall board having a body portion made of a gypsum plaster, a Portland cement product or a magnesite cement product that, at one stage of formation process, exists in the plastic state. The plaster may also include a resilient material such as cork or sawdust to prevent cracking of the panel when pierced by a nail, screw or other fastener. A mesh material such as cotton gauze, wire cloth or perforated paper or fabric is applied to both sides of the body portion while it is in the plastic state.
U.S. Pat. No. 3,284,980 (Dinkel) discloses a hydraulic cement panel having five separate elements that include two thin, high density hydraulic cement surface layers in each of which is embedded a fiber mesh, and a thicker core of low density cellular hydraulic cement laminated between the thin, high density surface layers. This panel is intended for use as wall board and may be used in damp environments for constructions such as shower stalls, bathroom floors, swimming pools and the like.
U.S. Pat. No. 3,466,822 (Hull et. al.) discloses concrete structures which are strengthened and rendered self-healing by reinforcement with embedded cross-laid groups of pretensioned yarns. This layer of yarns is disposed midway through the thickness of the panel.
Though the Dinkel and Hull et. al. Patents disclose panels which are somewhat flexible and, hence, are said to be less susceptible to damage during transport and storage, none of the patents cited above describe cold workable panel structures which are used after they have been cold formed to make curved structures and articles having a relatively small radius of curvature. None of these patents disclose methods for producing such panels. Moreover, none of these patents disclose any relationship between the tensile strain of any reinforcing layer to the compression strain of the reinforced panel core during cold deformation.
Other flexible building panel structures are shown in U.S. Pat. Nos. 2,070,527 (Elmendorf); 2,869,182 (White, Jr.); 3,084,403 (Elemdorf); and 3,607,605 (Suzukawa). Still other structural elements are disclosed in U.S. Pat. Nos. 2,252,980 (Rhett); 2,312,293 (Weiss); and Re. 27,061 (Rubenstein). However, none of these patents disclose a cold formable, reinforced panel structure which has a unitary, non-segmented panel core made from a cementitious composition.
Water retentive cementitious compositions suitable for use in the present invention are disclosed in U.S. Pat. No. 3,762,937 to Morris Schupack, the present inventor. This composition has been used for grouting post-tensioned tendons.